<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    table {
      border: 1px solid #000;
      text-align: center;
      width: 240px;
    }

    th,
    td {
      border: 1px solid #000;
    }

    h3 {
      position: relative;
    }
  </style>
</head>

<body>

  <div id="app">
    <h3>小黑的礼物清单</h3>
    <p>礼物总数：{{ totalCF()}} 个</p>
    <p>礼物总数：{{ totalCF()}} 个</p>
    <table>
      <tr>
        <th>名字</th>
        <th>数量</th>
      </tr>
      <tr v-for="(item, index) in list" :key="item.id">
        <td>{{ item.name }}</td>
        <td>{{ item.num }}个</td>
      </tr>
    </table>

    <!-- 目标：统计求和，求得礼物总数 -->
    <p>礼物总数：{{total}} 个</p>
    <p>礼物总数：{{total}} 个</p>
    <p>礼物总数：{{total}} 个</p>
    <p>礼物总数：{{total}} 个</p>
  </div>
  <script src="https://cdn.jsdelivr.net/npm/vue@2/dist/vue.js"></script>
  <script>
    const app = new Vue({
      el: '#app',
      data: {
        // 现有的数据
        list: [
          { id: 1, name: '篮球', num: 1 },
          { id: 2, name: '玩具', num: 2 },
          { id: 3, name: '铅笔', num: 5 },
        ]
      },
      methods: {
        totalCF() {
          console.log('函数被调用了！')
          const arr = this.list.reduce((sum, item) => sum + item.num, 0)
          return arr
        }
      },
      // computed中的计算属性会提升性能，因为计算属性是依赖数据发生变化时才执行，而methods中的函数是每次都执行
      computed: {
        total() {
          console.log('计算属性被调用了！')
          const res = this.list.reduce((sum, item) => {
            return sum += item.num
          }, 0)
          return res
        }
      }
    })

  </script>
</body>

</html>